There is no plan for an interim analysis done to inform whether stopping rules should be implemented because by the time an analysis of follow-up 2 data for cohort 1 is available then cohort 2 will already have experienced the intervention. Analysis of effects estimates will be done on an 'intention to treat' basis with all participants and controls originally recruited to the study plus any reserves brought into the programme to augment drop-outs being included in the analysis regardless of attendance in the programme. Logistic regression will be used to estimate effect sizes for binary outcomes and ANOVA for continuous measures. Each will generate crude and adjusted estimates, the latter adjusting for any significant (P<0.1) baseline differences in socio-demographic measures or baseline values of outcome measures.